This chapter presents a critical analysis of the feasibility of biodiesel production by comparing different production routes. Special emphasis is placed on the production of biodiesel from residual oil derived from corn ethanol production, known as Distillers Corn Oil (DCO). The analysis begins by defining what constitutes biodiesel and highlighting its advantages over fossil-derived diesel. It then addresses the need for sustainable processes to replace fossil energy sources and explores how circular economy principles and the United Nations Sustainable Development Goals (SDGs) can be advanced through the use of biodiesel produced from DCO via an enzymatic route. The study proceeds with an evaluation of existing reaction pathways—basic homogeneous, acidic homogeneous, CaO/SiO heterogeneous, KOH heterogeneous, and enzymatic—and discusses the advantages and disadvantages of the enzymatic route in particular. Finally, a comparative life cycle assessment of fossil diesel and biodiesel is presented.